This invention relates to repair clamps for pipelines and, more particularly, to a repair clamp for small diameter pipes which will effect a complete circumferential seal around a portion of the pipe to be repaired.
A typical pipe repair coupling for small diameter pipes includes a cylindrical elastomeric gasket having an axial split therein which is adapted to be placed over the portion of the pipe to be repaired. A clamping band exerts compressive forces on the gasket to seal the gasket against the pipe. The clamping band is a flexible steel band having lugs at its ends which are drawn toward each other by a nut and bolt assembly to apply tension to the band. An arcuately shaped armor sleeve is provided which conforms to the shape of the gasket and which serves to cover at least that portion of the gasket which is not directly engaged by the clamping band so that the compressive forces are uniformly applied to the gasket.
One such pipe repair clamp is shown and described in U.S. Pat. No. 4,676,275. According to that patent, a gasket in the form of a sealing cartridge is enclosed within the confines of a metallic outer strip or band, to the ends of which, lugs have been secured. The sealing cartridge is comprised of a cylindrical axially extending gasket which has an axially extending hinge portion integral with and of the same material as the gasket and which is axially split or disconnected so as to provide axially extending free end portions at a point approximately 180.degree. displaced from the hinge portion. Two armor sleeves of substantially semi-cylindrical shape and co-extensive in axial length with the gasket are bonded to the exterior of the gasket. Each sleeve extends from the region of the hinge portion to a point just short of a respective free end of the gasket with which it is associated. With this arrangement, the free ends of the cartridge, that is the free ends of the gasket and armor sleeves, may be rotated about the hinge portion without deformation of the sleeves to permit the cartridge to be mounted on the pipe to be repaired or the pipes to be joined together. On the pipe, the free ends of the cartridge are brought together and the exterior metallic band is mounted around the cartridge and stress applied thereto by tightening the lug bolts.
Since the metallic outer strip of the sealing cartridge is disconnected to provide free end portions at diametrical points on the gasket, the clamping band must be carefully aligned with the cartridge to ensure that the clamping band will exert confining pressure on the exposed portions of the gasket. If the band is misaligned the gasket will tend to extrude at the hinge portion or at the portion where the free ends of the gasket meet. Furthermore, even if the clamping band is properly positioned during the initial stages of installation, the band may become displaced as the clamping bolt is tightened.